Thermionic tube



Dec. 5, 1950 P. M. CUPIDO ET A1.

THERMIONIC TUBE Filed July 2o, 194e BEE A 0. wzzzzzzwhmw..

Patented Dec. 5, 1950 UNITED STATES PATENT OFFICE THERMIONIC TUBE Application July 20, 1946, Serial N0. 685,158 In Belgium May 1, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires May 1, 1965 (Cl. Z50-27.5)

15 Claims. 1

In the use of thermionic tubes it is generally of great importance that each tube can be replaced by a tube of the same type without any need for modification of the apparatus in which the tubes are used. By the latest methods thermionic tubes may be manufactured in such a manner that substantially all the important characteristic magnitudes of several tubes of one type are equal within very narrow limits. It has been found, however, that as regards the capacities between the electrodes and with respect to the surrounding parts of the apparatus the permissible tolerances are so small that mass production of tubes which are interchangeable without further expedients is in practice impossible without involving excessively high manufacturing cost. This applies particularly to tubes intended for short waves.

It has been previously suggested that thermithe desired value with respect to one another. l

This operation requires great skill, which naturally results in an appreciable increase of the cost of the tube.

A thermionic tube according to the invention comprises a screening means and contains a trimmer condenser located in a space bounded in part by the wall of the bulb and in part by the screening means.

Wherever in the foregoing and hereinafter reference is made to the screening means of the tube, we mean thereby either an electrically conductive envelope which may be firmly applied to the wall of the tube, for example by the spraying process, or a conductive sleeve which is so slipped on the tube as to be clamped thereto., We mean thereby, in addition, a coating which may be applied, if desired, to the bottom of the tube through which the supply conductors for the electrodes are led in an insulating manner.

For discharge tubes having a flat bottom the last-mentioned part of the screening means takes the shape of a dish provided with apertures for the passage of the supply conductors. In each case the screening means constitutes an integral part of the tube. It need not, however,

cover the Whole of the wall of the tube but may extend over a portion thereof.

A thermionic tube according to the invention permits of obtaining appreciable advantages with respect to the above-described tube of known type. By placing the trimmer condenser in the space described, the capacity of the condenser on trimming the latter is not affected by the hand of the person carrying out the trimming operation. Furthermore, an important advantage is that the trimmer may be arranged in a dust-proof manner and is safeguarded against mechanical damage. The tube once trimmed thus always retains the same constants during its use. Furthermore, the screen prevents the trimming from being affected by elds located outside the tube, which is of special importance when the tube is inserted into the holder, since every holder has some influence on the capacities of the contact members and hence on the capacities of the electrodes. In the tube according to the invention the influence of the tube holder on the capacities is suppressed completely.

In the above-described known tube with trimmer electrodes which are constituted by a conductive coating on the bottom of the tube, it is not possible to provide afterwards a screening means at the bottom of the tube, since such a screening means would result in a strong variation of the capacity already adjusted.

Numerous forms of construction of a trimmer condenser which may be used in a thermionic tube according to the invention are possible. The size of the condenser is of great importance since the dimensions of the tube are preferably kept down as much as possible. Since only the trimming of very 10W capacities is concerned, very small condensers are sufcient indeed, which consequently may be easily arranged between the screening means and the bulb.

In one particularly advantageous form of construction of a thermionic tube accordingA to the invention one electrode of the trimmer condenser is connected to the screening means. As a particular case thereof we must see a construction in which part of the screening means itself serves as one of the electrodes of the condenser. This form of construction is, as a rule, not serviceable for ultra-short waves, since in this case it is desirable that one of the electrodes of the trimmer condenser should be connected directly to the cathode.

In another form of construction one of the electrodes of the trimmer is constituted by pari? of the supply conductor of the electrode whose Vcapacityis to be adjusted. This construction is very simple since in this case only one additional electrode for the condenser need be provided.

In a further form of construction of the ther-- mionic tube according to the invention the tube comprises aV so-called flat bottom, by which we mean a closing member which is more or lessv plate-shaped. It need not be mathematically plane, however, but may exhibit some grooves, rims or protrusions. If this t'ube is provided at the bottom with a screeningmeans, the trimmer is preferably placed between the screening means and the Vbottom of the tube. of the trimmer is connected to the screening means, use may be made with great advantage of that construction in which a part of. the screening means constitutes one of the electrodes of the condenser.

The movable part of the trimmer may be connectedeither tofthe supply conductor whose capacity is to be regulated. orto the other electrode -with which thel condenser is connected, for examplethe screeningmeans. The latter form of construction affords the advantage that the movable partfhas a xed potential and, consequently, the trimming is not affected by the use ofY atool, for example a screwdriver, for the adjustment of the trimmer.

In a--highly advantageous form` of construction of -a tube according-to the invention the vmovable partoi the vtrimmer is constituted by the dielectric.. This means that between the conductive electrodesofy the trimmer there is provideda. fixeddielectric which may be brought more or less between the plates, the dielectric in.this. case: consisting partly of .air and partly ci the iixed insulating material.

In` a particular form Vof construction` one electrode-of the trimmer is constitutedby a :conductive rod or-str-ip connected to the supply conductor ofu the electrode to be trimmed. As an alternative, i one oiV the electrodes ci the trimmer may be applied to the insulating wall of the" tube round the supply conductor of an electrode and anelectric contact with the'latter.

For fixing the movable partofthe condenser againstdisplacement subsequent to the trimming operation, use may bemade of a cementing material; this manner of fixing is already known in itself.

The invention will now be explained more fully by severalY practical examples shown diagrammatically inFigures 1 to 13, inclusive, of the accompanying drawing. These figures show a portio-n of a tube closed by a plane bottom plate whichis fixed to the bulb, for exampleybyv iu.- sion. In all the'iigures one of the electrodes. is connectedto the screening means. The invention-is however by no means limited to tubes of this kind.

In lFigure 1 the trimmer is a so-called tube trimmer.

AIn Figure 21a portionof a supply conductoris also apart oflthetrimmer condenser. The same isthecasein the formsof construction shown in Figures 34' and 5.

In Figure 6 the trimmer is a wire trimmer, while Figures '7 up to- 13 inclusive show trimmers constitutedby two or more parallel plates.

In Figure 1, reference numeral iV denotes the glass walloflth'e tube which is closed by the glass b'ott'om 2,' in which the supply conductors 3 of the system of electrodes, not shown. are xed in a vacuum-tight manner. The bulb ofthe tube is If one side surrounded by a metal bushing 4, the bottom of which adjoins a metal dish 5 by which the tube is screened at the bottom. The supply conductors 3 are freely led through apertures formed in dish 5. The supply conductor 3 is provided with a transverse rod 7 which is xed to it at 3, for example, by spot-welding. Rod 'i is surrounded by an insulating sleeve Si which is iixed on it. The insulating sleeve 9 is surrounded by a-metal sleeve it which is slipped over sleeve e and connected at i i to screening dish 5 by means of a exible wire. The latter is freely passed through an aperture i2 so that sleeve l may be shifted around sleeve 9 likewise through the aperture l2 with the aid of a ne tool. Owing to the fact that a larger or smaller portion of sleeve IQ thus comes opposite the rod l, the capacity of the electrode connected to the supply conductor is adjustable within certain limits.

In Figures 2 up to 13 inclusive identical parts of the thermionic tubeare indicated by the same reference numerals.

Figure 2 shows a portion of a tube in which a trimmer condenser of very simple construction is provided between the glass closing plate and the dish-shaped screening means. The trimmer is constituted by a curved plate i3. which is secured to dish 5 at lli. A portion of supply conductor 3 serves as the counter-electrode for plate i3; through aperturey I2 the latter-may be bent more or less towards conductor 3 with the'aid of a tool.

Figure 3 shows a portion of a tube in which a wire trimmer is used. This is constituted byV a conductive wire i5 helically wound on an insulating sleeve IS.' The latter surrounds supply conductor 3, a portion of which consequently serves'as'anelectrode' of the condenser; The free end of the wire i5 is led through aperture l2 and secured to the dish-like screening Ymeans at" Il. When pulling the part of the wire lewhichv is passed'through the aperture, the sleeve it' turns aroundsupply conductor?, due towhich anpor'- tion of the wire is wound off and the capacity of the condenser` decreases. The wire 45u/nay be fastened to sleeve l'in known manner by means of athinA lacquer layer. 'Io facilitate the turning motion round conductor 3, a-second sleeve may be provided between the latter and sleeve I6.

In Figure e the trimmer is constituted by a flanged sleeve l1 arranged'so as to be slidable around supplylconductor 3. Between conductor 3 and sleeve I1 is an insulating material Id'which may consist of some plastic material or other which-hardens by local heating or, for example, under` theV action of air. Sleeve i1 is connected to screening means 5 at i9. Thesecond electrode of the trimmer is constituted by' a conductive layer 2! applied round supply-conductor Sto the bottom 2 of the tube. The conductive layer 2li mayconsist, for example, of a sticked metal foil or a silver coating on the bottom 2 of the tube. It is applied so as to be in electrically conductive contact withlsupply conductors 3. By shifting sleeve i1 along supply conductor -3 with the aid of an instrument passed through aperture. 2! of dish 5, the capacity ofthe trimmer is adjusted.

In Figure 5, part of supply conductor 3,con stitutes one electrode and sleeve '22 constitutes the other electrode of the trimmer condenser. A plastic material 23 is provided between the two electrodes. Sleeve 22 is connectedto the screening means l at 2li. The trimmer is adjust-ed' to the correct value by deformationof vaca-'sacas sleeve 22, for which purpose the material 23 must be plastic. Consequently, use is preferably made of some material or other which hardens after being treated, for example a hardening cementing material. Since the deformation operation must be effected with the aid of a pair of tongs or a similar tool, this construction is not suitable for a tube utilising a dish-like screening means. In order nevertheless to obtain a screening means for the lead-through conductors, bushing 4 surrounding the bulb of the tube is caused to protrude downwards.

Figure 6 shows a form of construction in which use is made of a wire trimmer which surrounds, in contradistinction to the form of construction of Figure 3, a transverse rod 25 xed to supply conductor 3. The wire is led to the exterior through an aperture I2 and secured to the screening means at Il. Since in this case the direction in which the wire is pulled during the L trimming operation is the same as that of the electrode 25, the insulating sleeve must naturally be rmly fixed to the rod 25 or at least be locked against sliding off this rod.

In Figure 7 one electrode of the trimmer is contheelectrode to be trimmed with respect to the screening means 5 may be adjusted. The shifting operation along conductor 3 may be effected, for example, with the aid of an instrument which is passed through aperture 21. An insulating plate 28 may be provided between plate 26 and the screening means 5. The dielectric of the condenser in this case partly consists of air and partly of an other insulating material. In this construction a satisfactory contact between conductor 3 and plate 26 must be ensured.

Figure 8 shows a modification of the construction of Figure 7, in which plate 26 is shifted by turning instead of by sliding. To this end conductor 3, together with the hole in plate 2E are threaded at 29.

Figure 9 shows a form of construction of al trimmer which does not substantially bring about any increase of the dimensions of the tube. One electrode of the trimmer is in this case constituted by a coating 33 on the bottom of the tube round supply conductor 3 and in electric contact with the latter. The other electrode of the condenser is -constituted by a part of the screening means 5. An insulating plate 3l, which can turn about conductor 3, is provided between the two electrodes. Owing to the particular shape of this plate and that of the conductive coating 30 it is possible by turning the plate to bring a larger or smaller part thereof between the condenser electrodes. Consequently, in this case the air dielectric is` replaced by the insulating plate, due to which the capacity of the condenser is varied. Since plate 3l and coating 30 may be given ,any arbitrary shape, it is possible to obtain a denite manner of variation. This figure and Figure l0, which is a bottom view of the trimmer, show in addition in what manner plate 3|' is accessible through an aperture 32 provided in the wall of the tube. This aperture -9` and 1 0 rstly lies in the exceptionally small dimensions and, in addition, in the fact that in this case an insulating part is turned. A satisfactory contact with the fixed electrode of the condenser is thus always ensured. In a particular form yof construction of this condenser apertures of determined shape may still be formed in insulating plate 3|.

Figure ll shows` a form of construction of a trimmer in a tube according to the invention in which the movable part, the rotor of the condenser, is constituted by a conductive plate 33 which is rotatably arranged around supply conductor 3 and in electric contact with it. An insulating disc 34 (Fig. 12) exhibiting an aperture 35 of any arbitrary shape is provided between plate 33 and the screening means, a portion of which serves as the second electrode of the condenser. As can be seen from the plan of the condenser in Figure l2, the conductive plate 33 approximately has the shape of a hemisphere. By turning this plate, which may be effected through aperture I2, opening 35 provided inplate 34 is covered more or less, due to which the capacity of the trimmer condenser varies. As before, in this construction a satisfactory contact between plate 33 and supply conductor 3 must be ensured. In one particular form of construction, which is not shown, the aperture may alternatively be formed in the screening means which serves as an electrode of the trimmer. Turning plate 33 over disc 34, which in this case need not have any aperture, has the effect of changing the total surface of the opposite electrodes of the condenser. From this ensues a variation in capacity.

The forms of construction of tubes according to the invention shown in Figures 1, 2, el., '7, 8, 9, 10, ll, l2 and 13 afford more particularly the advantage that the movable part 'of the trimmer condenser is adjustable in two directions. Consequently, the exact position of the trimmer may be found very accurately by moving this part to and fro.

As a matter of fact, numerous forms of construction of trimmers in addition toI those shown in the figures are possible.

What we claim is:

l. A thermionic tube comprising a bul-b portion having a wall member, a supply conductor secured in said wall member of said bulb portion, a screening means mounted on said bulb portion and also having a wall member, said Wall member of said bulb portion and said wall member of said screening'means forming a spacing, and a trimmer condenser positioned in said spacing formed by said wall members, said trimmer condenser having rst and second electrodes and a dielectric therebetween, one of said electrodes being in direct electrical contact with said screening means.

2. A thermionic tube comprising a bulb portion having a wall member, a supply conductor secured in said wall member of said bulb portion, a screening means mounted on said bulb portion and also having a Vwall member, said wall member of said bulb portion and said wall member of said screening means forming a spacing, and a trimmer condenser positioned in said spacing formed by said wall members, said trimmer condenser having first and second electrodes and a dielectric therebetween, one of said electrodes being in direct electrical `contact with said screening means, the other of said electrodes being -constituted by a portion of the said supply conductor. v

3. A thermionic tube comprising a bulb por- 'aseegsse f 'tion having: 'a wal1.= member,.za supply'conductor secured ini said; wallmeniber' ofv said bulb` pors tion', ai screeningl meansimounted.` on said' bulb portion and; also' having. a'wall' member, said Wall memberof said bulb portion and said' wall memberfof said screening means'forming a spa-ciing, and a trimmer condenser positioned insald spfacingiformed: by said wall membelisaid. trimmer; condenser havingA an movable and ai xed electrode and;Y a dielectric therebetween, said movable electrode being electrically. connectedto said supply conductor and said" xedf electrode beingVV constituted by said screening means.

iii-Az thermionic tube: comprising. a bulb'- portion having a wall member; asupply conductor secured in said wall member of said. bulb' por tion, 'a screening means mounted onsaid bulb portion and alsoY having axwall; member: said wall'member'of saidbulb portion andisaid wall member: of saidV screening means forming' a' spac= ing,- and a trimmer'condenser. positioned in: said vspacing formedbysaidwall members, saidtrimmingcondenser 'havingirstand second` electrodes and' a movable'dielectric therebetween, one of said electrodes being in directelectrical contact l :with said screeningmeansf.

, 5; A thermionic tube comprising bulb'por'- tion. havingiarwall member, a supply conductor secured `insaidwall member of` said bulb portion, a screeningy means mounted on said bulb "portion and: also having' a wall-member, said wall mem'- bcr cfs-aid bulb portion'ands'aid'wall memberY of .said screening means'- forming: a' spacing; and.` a trimmer' condenser; positioned. in said spacing formed by said Wall members, said trini'm'eiic'ondenser. having t a'. movable and a` fired'. electrode and 'ai dielectric' therebetween, said movable electrode: being-indirect electrical Contact with said screening means.

6. A. thermionic tube.' comprising a bulb portion having'a wall-member, a supply conductor vsecured i'n saidwall membenofsaidbnlbiportion, a screening means mounted on said bulbp'ortion and alsoh'avingawall member, saidffwall mem- Aber of saidbulb lportiona-nds'aid screening means forming a spacing, and"v af trimmer' condenser positioned in said spacing formed by saidwall members, saidr trimmer condenser having first 'and-'second'electrodes and a dielectric therebetween, one of said electrodes being in 'direct electrical contact with said screening'means, the other of 'said' electrodes being-constituted by an elongated conductive element in electricalY connection Vwithithe said* supply'con'duct'or;

'7; Ai thermionic` tube comprising a bulb` por; tionihavinga' wall member, a'V supply'condu'ctor As'e'cure'd'in said wall member ofsaidbulb portion, @screening means mounted'on said bulb portion andfalsohaving a..wall`member, said'wall mem; ber'o'saidzbulb portion and saidwall memberof "saidiscre'ening means forming a spacing, and a trimmer condenser positioned" in said spacing formed by said'wall members; said trimmer condenser having rst and'second electrodes and a dielectric.. therebetween, one of` said electrodes being' in direct electrical' contact with said screening means, the other 'of'said electrodes being constitut'edby an electrically conductive 'coating positioned on saidwall member of said bulb portion andsurroundingsaid supply condctorand in electrical contact therewith.

8:. A thermionic tube comprising a bulb por` tionhavinglawall membenza supply conductor.

secured in said wall member of said bulb portion, hafiscreanfing'. meansiniountedionesaidbulb portion andi also? having a; wall.. memben said v/al'l mme b'er of saidbulb portiomands yd.' wallirn'ember of.' said.Y screening'. means' forming a: spacing-1 and a trimmer condenser positioned? in said spacing formed by said walll n'iernberls,v said trimming condenser having-aj` rst electrode" constituted by a. transverse rod secured tofsaicll supply conduc-y tor, asecond` slidable electrode" s'urrounding'Y said rlrstelectrode and a dielectric'- therebetween erd tending coaxially oi said' rstv and second'4 elec'- trodes, the sldable electrode being' in direct electrical contact with .saidE s'reeningneansi 9. A' thermi'oni'e' tube' comprisingv a b'ulb' portionhaving awallme'mber, a supply conductcr secured in said wall ine'mber'oi` said lc'iiilb p'o'r-- tion, a screening means/mounted on said? bulb portion and also` having a Wall member, said Wall member of said bulb portiontand said wall member'of saidsc'reening means forming" asp'ao'jing, and a trimmer' condenser positioned in said spacing formed in said wall members, saiditrim'- mer condenser having al Vnrst electrode constituted by'a transverserodfsecured tosaid supply conductor, a second helically woundI conductor 'electrode and a dielectric'therebetween and" extending' coaxially of said rst and secondv elec; trodes, the said helically wound'conductor elec# trode being in direct electrical contact with said screening means.

10. A thermionic tube comprisinga bulb por-- tion having a wall member, a supply conductor secured in said wall member of: saidv bulb por-v tion, a screening means'mount'ed 'on' said bulb portion and also having a wall` member, said Wall member'ofsaid bulbV portion and saidwall member oi said screeningmeans forming'a spacf ing, and a trimmer condenser'positioned in' said l spacing formed by said wall members, said trim'- ming condenser having 'a rst electrode constituted by said supply conductor a second heli*- cally wound conductor electrode anda dielectric therebetween. extending. coaxially of said first and second electrodes, the said' helioally Wound conductor' electrode being. in' direct electrical contact with said screeningmeans.

l1. A thermionic tube as claimed'in claim 1 wherein the first of the said electrodes of the said-trimming condenser isin electricalfco'ntact with the said screeningmeans and the saidvsecond electrode is constitutedv by an' electrically conductive plate rotatable about the said supply conductor, theA dielectric between these' electrodes comprising an insulating plate having a shape such that rotation of the saidsecondelec'- trode varies thearea relationships'of said insu'- lating plate and said'second electrode'.

12. A thermionic tube asclaimed in claim' l1 wherein the said insulating plate has' an*v ap'eri ture therein whereby the portion oi'said apertureadjacent ther rotatable electrode is varied by the said rotation thereof.V

1G.' A thermionic tubey as claimed' in claimv l wherein the' iirst` of the said electrodes of the 'said' trimming condenseris constituted by the said screening means' and the said second` eleci trodeY isv constituted by a conductive coating 'positionedon the 'wall member'of/ said'bulb pon said-insulating. plate and the saidelectrc es:

"whereinA the: rst; ofi thevsaidelectro des oif the and having a flat bottom, supply conductors secured in said at bottom, a screening means having an aperture therein and including a metal cup element secured to said vessel at said flat bottom, said bottom and said element forming a. spacing, said supply conductors passing through said spacing and through the said element and in insulated relationship with said element, a trimmer condenser in said spacing and 20 comprising a movable electrode, said electrode 10 being adjustable through said aperture in said screening means.

PIET MARINUS CUPIDO. BERNARDUS OCTAVIANUS MARIA GALL. JOHAN LODEWIJK HENDRIK JONKER. ADRIANUS JOHANNES WILHELMUS MARIE VAN OVERBEEK.

REFERENCES CITED 10 The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date l5- 1,539,672 Holst May 26, 1925 1,683,202 MacDonald Sept. 4, 1928 1,879,544 Scognamillo et al. Sept. 27, 1932 1,923,552 Murphy Aug. 22, 1933 FOREIGN PATENTS Number Country Date 584,306 Germany Sept. 18, 1933 

